The purpose of this study is to determine if IL-IO, TGF-beta and TNF-alpha are present in B53 tumor ascites and then to determine if those cytokines present contribute to the impaired function of CD4+ T cells seen in B53 tumor-bearing mice. This murine plasma cell tumor model is similar to the human disease multiple myeloma, and increasing the understanding of the effects of tumor associated soluble factors on host cells in this murine model may lead to improved treatments for patients with multiple myeloma, which is at present an incurable malignancy. Presence of IL-IO, TGF-beta and TNF-alpha in tumor ascites supernatant will be determined by ELISA. The immunosuppressive potential of cell-free tumor ascites supernatant will be tested in an in vitro culture system using lymphocytes collected from peripheral and mesenteric lymph nodes of normal BALB/c mice. Functional capabilities of Conconavalin A stimulated T cells will be determined by assessment of proliferation and cytokine secreti on of 48-hour lymphocyte cultures treated with tumor ascites supernantant at final volumes of 1% and 5%. Decreased proliferation and decreased, secretion of the cytokines IL-2 and IFN-gamma compared to normal stimulated lymphocytes will indicate suppression of T cell function. Proliferation will be measured by the my modified MTT assay. Cytokine secretion will be determined by ELISA analyses of culture supematants. Effects of individual cytokines will be determined by titration of each cytokine in stimulated lymphocyte cultures and comparison of proliferation and cytokine secretion to that of normal stimulated lymphocytes. Neutralizing antibodies to suppressive cytokines will be tested in vitro. Abrogation of T cell suppression by neutralizing antibody treatement will confirm the importance of a suppressive cytokine in the observed T cell suppression in the B53 tumor system. Key Words: T cells, plasma cell tumor, regulation